How does a child's vocabulary change with age?

How does a child's vocabulary change with age? The data set vocab contains the average oral vocabulary size (words = number of words) for children at different ages (age) (taken from Discovering Psychology by Weiner, 1977). Plot the data first: in MATLAB plot(vocab.age,vocab.words,'*'), and in R or Splus plot(vocab$age,vocab$words). Then fit a straight line of words versus age , in MATLAB(lm(vocab) followed by model words=age), and in R or Splus lm(words~age,data=vocab). intercept = ------------- slope = -----------Estimate the average number of words at age 7= -----------